Safety switches are generally used to force the activation or deactivation of an electrical power supply. The fields of application of safety switches are legion. In the industrial as well as in the private domain, application scenarios such as, for example, a guard door, a protective cover, a safety fence or similar arrangements can be implemented with the aid of a safety switch.
In the present prior art safety switches of this kind have a basic structure, hereinafter also referred to as a housing, and a separate actuator. The reason for this two-part implementation is to be found in the way in which the safety switch is used. The separate actuator and the housing are mounted on separate mechanical units in order to be brought together for a specific operating state. Thus, for example, the separate actuator could be mounted on a movable door, whereas the housing of the safety switch could be fixed to a wall or a door frame.
The basic structure of the safety switch has a drive head and can be of single- or multipart design. Furthermore the switching contacts are arranged in the basic structure. The drive head has one or more openings into which the actuator is introduced in order, for example, to close opener contacts.
In the safe system state, which is given when the danger zone is screened off by way of a protective device, the actuator is located inside the drive head. If, for example, a guard door on which the actuator is disposed is opened, the actuator is extracted from the drive head, causing the system to be switched off, or placed in a safe state, as a result of the forced opening of the opener contact. If the system cannot easily be switched off or, as the case may be, the danger associated therewith cannot easily be eliminated, the safety switch can also be provided for the purpose of locking the guard door.
The precise insertion of the actuator proves problematic in the case of the mechanical actuation of the drive head by way of the actuator. Reliable introduction of the actuator into the drive head must therefore be ensured under mechanical load and the actuating function reliably triggered in spite of any deviations from the provided insertion path. This tolerance problem arises due to the fact that the drive head and the separate actuator are mounted on different carriers which allow a certain amount of play. This problem is generally exacerbated with exposure of the safety switch to wear and tear, as a result of improper handling of the protective device or due to deficient assembly right at the time of commissioning. It can be assumed that in the standard case the separate actuator has an unavoidable offset with respect to the insertion opening of the drive head. With the actuator inserted, therefore, the actuator must be able to be aligned in accordance with the insertion opening of the drive head.
Introduction of the actuator at an angle in the case of cover-like protection objects constitutes a further problem. This problem is based on the fact that protective covers, for example, are not actuated in a linear manner, as are sliding doors for example. The movement of a protective cover corresponds to a partial rotational movement about a rotational axis which is mostly determined by way of hinges. Consequently it must be possible for the actuator to be inserted into the drive head at a certain angle that requires to be set beforehand. In this way it is ensured that upon reaching an end position in the drive head the actuator is aligned with respect to the same in an operationally correct manner.
Flexible mounting of an actuator by way of rubber bushings likewise proves problematic. For example, actuators are often secured to a mounting surface by way of two screws, with the actuator plate being flexibly mounted by way of rubber bushings and consequently only being able to compensate to a very limited extent for tolerances between, for example, a guard door and a frame. Because the drilled holes in the actuator plate are typically very much larger than the screw heads of the fixing screws, actuators of this kind must generally be mounted by way of large-sized retaining washers. If the ratio of retaining washer to drilled hole in the actuator plate does not correspond (the retaining washer could be too small, for example), the rubber bushings can be moved over the screw head, thereby creating a safety risk. A further disadvantage with actuators of this kind is that a desired preferred direction can only be pretensioned with considerable overhead.
DE 295 16 230 U1 discloses a radius actuator which is mounted on an elaborate base member. Because of its base member the actuator's possible tolerance compensation is very limited. A lateral offset is not possible and in addition the base member has a large number of components.